Fiber treatment and product



Patented Sept. 27, 1938 PATENT OFFICE mma TREATMENT am) raonncT Joseph 1.. Goodale, Ipswich, Mass.

Serial No. 142,070

No Drawing. Application May 11, 1937,

Claims. (CI. 21-26)- The present invention relates to a treatment of best and structural fibers, whereby the fibers are rendered more resistant to attack by deleterious organisms, such, for example, as algae, bacteria and/or fungi, and to the resulting product.

The cells of both best and structural fibers consist essentially of cellulose in association with various alteration products, such as lignin, cemented together by a water-insoluble pectinous material and compacted to form an individual fiber. Examples of bast fibers, derived from the inner fibrous bark of dicotoledenous plants, are flax, ramie, jute, etc. Examples of structural fibers, derived from the stalks, leaf stems and leaves of moncotoledenous plants, are sisal, manila, sanseveria, etc.

It is an object of the present invention to provide an improved .methodof treating bast and structural fibers, whereby they are rendered more resistant to the damaging attacks of organisms, such for example as algae, bacteria and/or fungi. The invention also comprehends an improved fibrous product By the process of this invention a toxic compound of copper is deposited within the cementing substance of the fiber without significant impairment of the tensile strength of the fiber.

My treatment may advantageously be applied to bast and structural fibers or fabrics comprising such fibers, such, for example, as cordage,

sacking or other fabrics (the word fabric" being used in its broadest sense to designate any fabricated article or material) in any case where the fibers or fabrics are exposed to the attacks of algae, bacteria and/or fungi.

The attacks of algae, bacteria and filamentous fungi upon bust and structural fibers are the cause of great economic loss. The resulting deterioration of the fibers has been ascribed to the 1 action of the organisms upon the water-soluble constituents of the fibers, giving rise to various acid products which in turn act on the insoluble parts, changing them further into bacterial food.

The value of a toxic, in the case of vegetable fibers, depends not only upon its abflity to control the attacks of organisms, but also upon its harmlessness to the tissues, both at the time of impregnation anddurlng subsequent exposure.

Copper compounds are toxic to many forms of life, but their use in the class offibers under consideration has hitherto been unsuccessful, so far as I am aware. The failure to efiect a satisfactory impregnation without loss of tensile strength may be attributed tothe fact that cellulose is negatively charged, and the "cementing pectinous substance is readily hydrolyzed by acids. Permanent protection requires the fixation of the toxic in an insoluble form upon the cellulose. Penetration of the pectinous substance i by a soluble copper salt must therefore first occur and be followed by the penetration of a substance which will precipitate an insoluble copper com- P und within the fiber.

Insoluble copper sulfide is formed when a solution of a copper salt is treated with a solution containing sulfide ions. Since, however, copper sulfide is negatively charged, it'is not adsorbed by the negatively charged cellulose, unless the latter has first been treated with a mordant, i. e., a substance which will impose upon the cellulose a positively charged substance. While preliminary treatment with mordants can be applied to pure cellulosic fibers such as cotton, in the case of bast and of structural fibers, it has a deleterious hydrolytic effect upon the cementing substance, with resulting solution and disintegration, the fiber being thus broken up into its elements with a corresponding loss in tensile strength.

I have found that these and other diificulties may be avoided and that best and structural fibers may be effectively and satisfactorily treated to increase their resistance to deleterious organisms such as algae, bacteria and/or fungi if the fibers be first treated with a weak acid associated with a copper salt corresponding to the acid used, and subsequently treated with a soluble sulfide.

By this treatment copper sulfide is formed within the confines of the enveloping pectinous cement. This obviates the difficulty of application arising from the insolubility of copper sulfide if this compound be formed before impregnation. In my process, penetration of the fiber by thecopper solution first occurs, followed by penetration by the sulfide. Further, in my process the imposition of a mordant, which imposes a positively charged substance on the cellulose-and which isadvan- ,tageous in impregnation of the fiber, is accominvention shows no loss of the color imparted by the copper sulfide.

Acids suitable for use in my process should ionize less than 10% in normal solution. Acetic acid is preferred, but other weak acids which ionize less than 10% in normal solution may be used. For example, malic or tartaric acid may be used. These latter acids, however, will crystallize in the fibers and thereby weaken the structure unless the crystals are removed. Therefore, if acids which crystallize in the fiber are used,

the crystals should be washed out after the treate ment. To avoid this washing operation, it is preferred to use acids such as acetic acid which do not crystallize in the fibers.

As previously indicated, the copper salt to be selected is that corresponding to the acid used,

1. e., with an acetic acid solution copper acetate will be used. In such a solution there is present the common ion effect" by which the degree of ionization and momentary acidity or alkalinity of a slightly active acid or base are decreased by the addition of their salts. Acetic acid, for example, is but slightly dissociated (reaction a):

By adding the moderately ionized copper acetate to the acetic acid solution, I provide :an extra supply of acetate ions, thus; by the law of mass action, favoring reaction b in the above equilibrium. Thus the small momentary acidity of the acetic acid is still further decreased and its reserve acidity is increased, while the total acidity remains practically unchanged.

Hydrogen-ion measurements show a pH value of N/ acetic acid of 2.9; of normal copper acetate in N/20 solution of 6.6. A mixture containing the same amounts of the two shows a pH of 4.8. Tests on various fibers finely shredded gave the following:

. pH Jute 4.2 Sisal 4.6 Ramle 4.6 Manila 4.8 American fia 4.8 American hemp 4.8

ions and adsorbs the copper sulfide precipitated by the subsequently applied sulfide solution.

My process provides a valuable method of precipitating a toxic compound of copper within the cementing substance of the fiber and causing the toxic to become fixed upon the cellulose without impairment of the tensile strength.

As previously indicated, my process comprises treatment of the fibers with a solution of a' weakly ionized acid and its corresponding copper salt, followed by the application of a soluble sulfide (such, for example, as hydrogen sulfide) or a solution containing sulfide ions, whereby copper sulfide is deposited upon and within the structural elements of the fiber.

As a specific example of one suitable procedure, the following may be given, it being understood that this is by way of example only and is not to be construed in a limiting sense: The fibers are immersed in a N/lO solution. of acetic acid and a N/20 solution of normal copper acetate for sevwith an acid which in normal solution ionizes less than 10% and with a copper salt corresponding to the acid used, then treating the fiber with a soluble sulfide.

2. The method of treating bast or structural fibers which comprises impregnating such fiber with a solution of an organic acid which in normal solution ionizes less than 10%, said solution also containing a salt of copper corresponding to the anion of the acid, and subsequently impregnating the fiber with a solution containing sulfide ions.

3. The method of treating bast or structural fibers which comprises treating such fiber with a solution comprising acetic acid and copper acetate, then treating the fiber with a solution containing sulfide ions, whereby the resistance of the fiber to attack by deleterious organisms is increased.

4. The method of treating bast or structural fiber to render the same more resistant to attack by deleterious organisms, which comprises treating the fiber with a solution comprising acetic acid and copper acetate then treating the fiber with a solution of mono-sodium sulfide.

5. The treatment of bast or structural fiber to increase the resistance of the fiber to attack by deleterious organisms, which comprises immersing the fiber in a solution containing acetic acid and copper acetate, rinsing the fiber, impregnating the fiber with a solution of a soluble sulfide, then rinsing and drying the fiber.

6. The treatment of bast or 'structuralfibers which comprises immersing the fibers in an approximately N/10 solution of acetic acid and an approximately N/20 solution of copper acetate at a temperature between approximately 60 and 80 F., agitating the liquid, and subsequently immersing the fibers in an approximately N 10 solution of mono-sodium sulfide.

'7. As a new article of manufacture, a fabric comprising fibers which consist essentially of cellulose-associated with water-insoluble pectinous material, said fiber being of substantially unimpaired tensile strength and containing copper sulfide. I

8. As a new article of manufacture, bast or structural fiber of substantially normal tensile strength, said fiber containing copper sulfide within the cementing substance of the fiber.

9. A process for the treatment of bast or structural fiber which comprises treating the fiber with an acid which in normal solution ionizes less than 10% and with a copper salt corresponding to the acid used, then treating the fiber with hydrogen sulfide.

10. The method of treating bast or structural fiber which comprises treating the fiber with acetic acid and copper acetate, then treating the fiber with hydrogen sulfide.

JOSEPH L. GOODALE. 

